The present invention relates to a dry end or a machine for the manufacture of a fiber web, and particularly to means which improve the web transfer from one dryer group to the next one, particularly a paper web. The invention proceeds from a dry end having two successive single tier dryer groups, with one group drying one side of the web and the other group drying the other side of the web. Each group of dryers has a respective web support belt passing around it. The web is transferred from the support belt of the preceding dryer group to the support belt of the succeeding group.
With respect to the state of the art, reference is had to the following publications:
Federal Republic of Germany Utility Model corresponding to U.S. Ser. No. 07/825,395 and European Patent publication 0426607, corresponding to U.S. Pat. No. 5,101,577.
The invention relates to a dry end which has at least two single-tier dryer groups and in which the one side of the web comes into contact with the cylinders of the one dryer group and the other side of the web with the cylinders of the other dryer group. In other words, the so-called separation place where the web transfers from one dryer group to the other is developed as a place of reversal. Two dryer groups of this type can be arranged in the initial upstream region of a dry end, where, therefore, the web to be dried is still relatively wet. It is entirely possible for a large number of dryer groups to be arranged one behind the other, each with a respective place of reversal between two adjacent dryer groups. If necessary, the entire dry end of a paper manufacturing machine can be divided into dryer groups in the manner that all places of separation are developed as reversal places. However, it is also possible to provide, for instance, two or three dryer groups with places of reversal only in the end region of the dry end. In such case, several dryer groups are connected one behind the other in the initial region of the dry end, and all of the cylinders of these initial groups come into contact only with the bottom side of the web.
In the first mentioned reference above, the web travels on a meander-like path from the last cylinder of the first, dryer group the first cylinder of the second dryer group. Within that meander-like path, the web initially travels together with the, first support belt of the first group and then with the second support belt of the first group. For this, two deflection suction rolls are required, each of which must have a very large suction zone (the suction zone must extend over more than half of the circumference of the roll). The amount of air to be drawn off is therefore relatively high. Furthermore, the arrangement requires a relatively large amount of space and therefore a relatively large horizontal distance between the said two drying cylinders.
According to the second reference an at least approximately linear path of travel from the last cylinder of the first dryer group to the first cylinder of the second dryer group is provided for the web which is to be dried. Since, however, the two support belts cover one another at the place where the web shifts from one support belt to the other, a relatively large distance is again required between the two dryer cylinders.
In accordance with FIG. 6 of the second reference, a space is provided between the two support belts which cover one another so that the web is transferred over a free travel path, i.e. without support, from one wire belt to the other. With regard to this, it is stated in that reference that said space makes it possible for the second support belt to travel at a higher speed than the first support belt so that the web is maintained under tension.